It is common to use databases to store significant quantities of data, especially in cases in which the data is shared by a number of database-accessing programs. Database-accessing programs that access data in a database may be executed on a number of different connected computer system. These programs issue a series of database transactions, each corresponding to one or more operations on the database, including read and write operations.
When two or more such programs are executed on the same computer system, they are typically each executed in a separate process. Each process corresponds to a set of resources provided by the operating system, most notably an addressable a range of memory, that is available only to programs ("threads") running within the process. Database-accessing programs are generally each executed in a separate process to prevent them from corrupting each other's data. Because database-accessing programs executing in separate processes cannot share data, the results of a read operation obtained by one database-accessing program are unavailable to other database-accessing programs that issue the same read operations. Indeed, because each database-accessing program typically discards the results of read operation performed as part of a transaction when the transaction completes, a single database-accessing program may have to issue the same read operation two or more times in a short period of time. These redundant transactions again must be applied directly against the database, which has significant time cost. First, the database-accessing program must transmit the transaction across a network to the computer system containing the database, which can take a substantial amount of time. Further, the to actually apply the transaction against the database, the database-accessing program must obtain the appropriate locks, or access controls, on the database, which can involve further network communication and synchronization with database-accessing programs executing on still other computer systems.
Further, because each process has an extensive set of resources devoted to it, the operations of creating and destroying processes each have significant time cost. In the conventional approach of executing each database-accessing program in a separate process, this significant time cost is incurred any time an database-accessing program begins or ends execution. In addition, many of the kinds resources devoted to separate processes are scarce, and allocating shares of these kinds of resources to each of a large number of processes further degrades the performance of the computer system and limits the number of other programs that can simultaneously execute on the computer system.
Given the significant disadvantages of the conventional approach to executing database database-accessing programs, an alternative approach to executing database programs that reduces redundant retrieval from database servers and reduces process overhead would have significant utility.